1. Field of the Invention
The invention relates to a dental isolation tray. More particularly, the invention relates to an isolation tray which is particularly suited for use when applying a dental sealant.
2. State of the Art
Dental sealants have been studied for many years and all studies have shown that the application of dental sealants to bicuspid and molar fissures is extremely effective in preventing tooth decay. Nevertheless, the procedure of applying dental sealants is still greatly under-utilized by dentists. The reason why most dentists do not utilize the procedure is that it is extremely difficult to perform properly and it is common to see multiple failures shortly after treatment. See, e.g., New York State Dental Journal, April 1992.
A dental sealant is a bonding liquid plastic resin which is applied to fissures in posterior teeth to seal them and thus prevent decay. The sealant is typically and economically applied to a contiguous group (quadrant) of teeth at the same time. However, it is critical that these teeth be isolated from the other teeth and kept scrupulously clean and dry during the application of the sealant. Achieving adequate isolation and dryness is very difficult. This is particularly so when treating children. Children generate more saliva than adults during dental procedures, they have a smaller mouth, and are not likely to remain still during a lengthy procedure. Commonly used devices such as cotton rolls and suction tubes do not provide adequate isolation or desiccation and they are unstable.
Rubber dental dams are well known for use in a variety of dental procedures. However, dental dams are also under-utilized because their use is time consuming, irritating and painful for the patient, and involves additional cost. See, e.g., Journal of the American Dental Association, Vol. 125, pages 81-82 (January 1994). The typical rubber dental dam is simply a rubber mat which is folded and inserted into a patient's mouth. Before insertion, a hole is punched in the rubber mat so that a particular tooth or group of teeth will be exposed when the mat is inserted. The inserted rubber mat is held in position by a frame or a clamp or a combination of frames and clamps. The dental dam covers the patient's tongue, the roof of the patient's mouth, and the patient's cheeks. It is easy to appreciate why a patient would be uncomfortable with such a device installed. Moreover, installation of the rubber dam requires a substantial amount of skill. The hole must be punched in the proper location and the dam must be properly located in the patient's mouth.
A different kind of dental dam is disclosed in U.S. Pat. No. 3,772,790 to Swan-Gett et al. This dental dam is described as a tooth isolating shield having two hinged semi-rigid dentition bridge conforming members, each connected to a soft deformable apron. A layer of cushion deformable material lines each of the semi-rigid members. One of the semi-rigid members is molded or fitted to closely conform to a patient's upper arch and the other is molded or fitted to closely conform to a patient's lower arch. Spring wires are embedded in the semi-rigid members at their hinged connection to bias them apart from each other. The lower semi-rigid member is provided with a fluid conduit extending about its lower periphery. The conduit is provided with a plurality of spaced apart holes and a centrally located fitting for connection to an aspirator. Before installing the shield in a patient's mouth, the practitioner cuts an opening in the proper location on the shield to expose a particular tooth or group of teeth which will be treated.
The dental shield disclosed by Swan-Gett et al. must conform well to the patient's upper and lower arches so that it will be held in place during the procedure. In practice, however, close fitting of the shield with the arches is very difficult. Arch forms vary greatly in length, width, and shape (square to V-shaped). Moreover, misalignment of individual teeth hamper the fitting procedure. In addition, many patients have mismatched jaws, e.g. cross-bites in the anterior or porterior regions or overjets (buck teeth), which can preclude fitting this type of shield. At the very least, in order to accommodate a variety of patients, a very large stock of different sized shields must be maintained.
Because of the close fitting requirements of the Swan-Gett et al. shield, the time required to install the shield will be prolonged. Many trial and error attempts will have to be performed in order to find the right size shield for a particular patient. Each shield which is tried and not chosen must be re-sterilized or discarded, adding to the total cost of the procedure. Additional time is consumed by the marking and cutting of the shield to expose the operative tooth or teeth.
Swan-Gett et al. recommends that the shield be cut to expose the entire tooth, i.e. the buccal, occlusal, and lingual surfaces. However, exposure of the lingual surface is undesirable in a sealant application procedure since this exposes the tooth or teeth to contaminations. This is particularly so if more than one tooth is exposed. Theoretically, the shield could be cut to prevent lingual exposure, but this would require more time and great skill on the part of the practitioner. The close fitting requirement of the Swan-Gett et al. shield prevents access to the lingual surface without forfeiting isolation from the tongue.
Stability and retention of the Swan-Gett et al. shield depends chiefly on the cushion deformable material which lines the shield. The teeth, the cushion deformable material and the shield are all in intimate contact. Thus, water and air spray hitting these surfaces is deflected and creates an aerosol of contaminants which is aspirated only after the aerosol settles. The aerosol of contaminants poses a serious health risk to the practitioner. Some of the aerosol is deflected out of the patient's mouth and into the practitioner's face.
The Swan-Gett et al. shield is designed to hold the patient's mouth open with small springs in the hinges of the shield. However, this does not prevent the patient from biting and the patient must consciously avoid closing his/her mouth during the procedure.
Swan-Gett et al. provides an apron surrounding the shield to help direct fluid into the aspiration ports. The apron, however, tends to stretch the cheek mucosa of the patient and is quite irritating. In addition, the stretch cheek mucosa act on the apron to urge unseating of the shield.
All of these aspects of the Swan-Gett et al. shield also contribute to the overall bulkiness of the shield and resulting significant discomfort to the patient, and in particular to child patients.